Drivers: hv: vmbus: finally fix hv_need_to_signal_on_read()

Commit a389fcfd2cb5 ("Drivers: hv: vmbus: Fix signaling logic in
hv_need_to_signal_on_read()")
added the proper mb(), but removed the test "prev_write_sz < pending_sz"
when making the signal decision.

As a result, the guest can signal the host unnecessarily,
and then the host can throttle the guest because the host
thinks the guest is buggy or malicious; finally the user
running stress test can perceive intermittent freeze of
the guest.

This patch brings back the test, and properly handles the
in-place consumption APIs used by NetVSC (see get_next_pkt_raw(),
put_pkt_raw() and commit_rd_index()).

Fixes: a389fcfd2cb5 ("Drivers: hv: vmbus: Fix signaling logic in
hv_need_to_signal_on_read()")

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reported-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
Tested-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

path: root/net/wireless/db.txt

#
# This file is a placeholder to prevent accidental build breakage if someone
# enables CONFIG_CFG80211_INTERNAL_REGDB.  Almost no one actually needs to
# enable that build option.
#
# You should be using CRDA instead.  It is even better if you use the CRDA
# package provided by your distribution, since they will probably keep it
# up-to-date on your behalf.
#
# If you _really_ intend to use CONFIG_CFG80211_INTERNAL_REGDB then you will
# need to replace this file with one containing appropriately formatted
# regulatory rules that cover the regulatory domains you will be using.  Your
# best option is to extract the db.txt file from the wireless-regdb git
# repository:
#
#   git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-regdb.git
#